Gearbox health monitoring and fault detection using vibration analysis

Gear systems are used to transfer rotation or power transmission from one shaft to another in desired ratios and high efficiency. These factors can be satisfactorily achieved if there is no fault in the gears. Whenever a defect occurs in a gear system (e.g. pitting, abrasive wear, bending fatigue cracks) the performance of the gears deteriorate. Transmission of motion and power, therefore, cannot be transferred as demanded. As a result, occurrence of fatal defects becomes inevitable. The research work presented in this thesis focuses upon the early detection of localised and distributed pitting damages, and a real-time fatigue failure in a gearbox using vibration analysis. The gear pitting failure modes have been realistically simulated on a few tooth surfaces in differing degrees of fault severity. The tooth crack has been achieved due mainly to bending fatigue during the fatigue test. Real gear vibrations have been obtained from two different test rigs utilising a two-stage industrial helical gearbox. Classical processing schemes in the time and frequency domains have been firstly employed to obtain general characteristics of gear vibration. Continuous wavelet transform has been then used to obtain a scalogram from which both mean frequency and instantaneous energy variations are generated. Conclusions are drawn about the effective vibration monitoring of gearboxes and the ways of early detection.